A sandwich is seen as a healthy lunch choice for many Australians, but those two slices of bread could contain more salt than a packet of chips, a new study has found.

Researchers from The George Institute for Global Health analysed 1439 bread products from 2010 to 2017, including loaves, rolls, crumpets, bagels, English muffins and flat breads, and found that some loaves of bread contain more than a third of the daily recommended salt intake in just two slices.

Rye breads were found to contain on average 20 per cent more salt that targets set by the Australian Food and Health Dialogue (FHD), which recommended sodium in bread products to be reduced to 400 milligrams per 100 grams. The FHD is a project involving representatives of government, the health sector and the manufacturing industry, set up to create action plans and set targets for reducing consumption of risk-associated nutrients including saturated fat and sugar and salt, and increasing consumption of fruits, vegetables and whole grain foods

The George Institute study found flat bread such as wraps, naan, roti and tortillas also included "unnecessary high levels of salt", on average containing a third more salt than white bread.

The study revealed the loaves with the highest salt levels were Schwob's Dark Rye, with just once slice containing more than double the amount of salt as a serving of Kettles sea salt crisps (an average serving contains 0.55g of salt per 45g serving).

The study found that in general, leading bread manufacturers have decreased the level of salt in their bread product, including Coles ( from 501 to 398 mg/100 g), Aldi (464 to 386 mg/100 g), Woolworths (430 to 390 mg/100 g), George Weston (470-388 mg/100 g), Goodman Fielder (463-411 mg/100 g) and MEB foods (361-271 mg/100 g). However, it said this wasn't an across-the-board result, with the salt content increasing in the products of some brans, such as Mountain Bread Company (333 to 432 mg/100 g - up 30 per cent), Old Time Bakery (110 to 294 mg/100 g; up 167 per cent) and Freedom Foods (535 to 584 mg/100g; up 9 per cent).

Consumers should check food labels to check the salt content of bread.

While the study showed salt levels in bread have generally decreased by about 10 per cent in seven years, lead author Clare Farrand said too many commonly eaten products still contain excessive amounts of salt.

"There has been a clear and welcome drop in salt levels in bread, particularly in those products that were covered by the salt reduction targets. However, some breads still contain high levels of salt," Farrand said.

"We know that excess salt in our diet increases blood pressure and the risk of stroke and cardiovascular disease, so our findings are incredibly worrying - especially as many of the products that have the highest levels of salt are perceived by families as being the healthiest."

The results have been released to mark the 10th World Salt Awareness Week (March 20-26), organised by World Action on Salt & Health. The theme for 2017 is 'Salt: The Forgotten Killer'.

"The average salt reduction in average bread and rolls has been 10 per cent, so that's a move in the right direction, so I actually think that's a good thing," Charlton tells SBS.

"For most of the bread and rolls that are produced by the major manufacturers, such as Coles, Aldi, Woolworths, George Weston and so on, those have all reduced their salt content of their bread products, and I would suggest that those producers contribute the most to sales of bread.

"This analysis looks at sodium content of bread and flat breads, but it doesn't actually look at the proportion of sales of those products. So for example, if 80 per cent of the population are eating those breads from the major manufacturers and those breads comply, then we don't necessarily have a major problem with those few consumers who are buying the more boutique-style breads that seem to be higher in sodium."

In Australia, there are no mandatory salt targets for food manufacturers, just the voluntary targets set out in the FHD.

Charlton says she would like to see mandatory salt targets introduced in Australia, as they have been in countries like South Africa and Argentina, as well as clearer labeling of salt content on products.

"What I think the data is saying is really compare when you're at the supermarket like for like, and don't assume one brand is necessarily similar across all of its product range," Charlton says.

"In lots of school lunch boxes, parents give a sandwich thinking that's the healthy option, which it generally is, but keep a look out [for the salt content].

"The message mustn't be 'avoid bread', because bread is a staple and it provides fibre, and it also provides folic acid and iodine, which has to be added to the salt used in bread, by law, so particularly for children bread actually provides a fair amount of iodine that they require each day."